Question

Can a triangle with side lengths of 8, 15, and 17 be a right triangle?

Answer 1

Yes it is. 
Glad to help!

Answer 2

Yes, it can. You can work this out by using Pythagoras' theorem (a² + b² = c²).

Add up the squares of the two smaller numbers (8² + 15²) = 289

Square root the sum of the two squares and see if it matches the bigger number. (√289) = 17.